浴室喷头隐藏细菌，特别是分支杆菌Mycobacterium avium,对免疫功能损伤、囊性纤维化或是艾滋病（AIDS）病人、接受癌症治疗或近期器官移植病人就生死攸关了。 In what may be the scariest shower news since Alfred Hitchcock's "Psycho," a study says shower heads can harbor tiny bacteria that come spraying into your face when you wash. People with normal immune systems have little to fear, but these microbes could be a concern for folks with cystic fibrosis or AIDS, people who are undergoing cancer treatment or those who have had a recent organ transplant.

Researchers at the University of Colorado tested 45 showers in five states as part of a larger study of the microbiology of air and water in homes, schools and public buildings. They report their shower findings in Tuesday's edition of Proceedings of the National Academy of Sciences.

In general, is it dangerous to take showers? "Probably not, if your immune system is not compromised in some way," lead author Norman R. Pace says. "But it's like anything else - there is a risk associated with it."

The researchers offer suggestions for the wary, such as getting all-metal shower heads, which microbes have a harder time clinging to.

Still, shower heads are full of nooks and crannies, making them hard to clean, the researchers note, and the microbes come back even after treatment with bleach.

People who have filtered shower heads could replace the filter weekly, added co-author Laura K. Baumgartner. And, she said, baths don't splash microbes into the air as much as showers, which blast them into easily inhaled aerosol form.

It doesn't seem as frightening as the famous murder-in-the-shower scene in Hitchcock's classic 1960 movie. But it's something to be reckoned with all the same.

The bugs in question are Mycobacterium avium, which have been linked to lung disease in some people.

Indeed, studies by the National Jewish Hospital in Denver suggest increases in pulmonary infections in the United States in recent decades from species like M. avium may be linked to people taking more showers and fewer baths, according to Pace.

Symptoms of infection can include tiredness, a persistent, dry cough, shortness of breath, weakness and "generally feeling bad," he said.

Shower heads were sampled at houses, apartment buildings and public places in New York, Illinois, Colorado, Tennessee and North Dakota.

The researchers sampled water flowing from the shower heads, then removed them, swabbed the interiors of the devices and separately sampled water flowing from the pipes without the shower heads.

By studying the DNA of the samples they were able to determine which bacteria were present.

They found that the bacteria tended to build up in the shower head, where they were much more common than in the incoming feed water.

Most of the water samples came from municipal water systems in cities such as New York and Denver, but the team also looked at shower heads in four rural homes supplied by private wells. No M. avium were found in those shower heads, though some other bacteria were.

In previous work, the same research team has found M. avium in soap scum on vinyl shower curtains and above the water surface of warm therapy pools.

And stay tuned. Other studies under way by Pace's team include analyses of air in New York subways, hospital waiting rooms, office buildings and homeless shelters.

The research was funded by the Alfred P. Sloan Foundation and the National Institute of Occupational Safety and Health.

Virginia Tech microbiologist Joseph O. Falkinham welcomed the findings, saying M. avium can be a danger because in a shower "the organism is aerosolized where you can inhale it."

In addition to people with weakened immune systems, Falkinham also cited studies showing increased M. avium infections in slender, elderly people who have a single gene for cystic fibrosis, but not the disease itself.

Two copies of the gene are needed to get cystic fibrosis, but having just one copy may result in increased vulnerability to M. avium infection as people age, said Falkinham, who was not part of Pace's research team.

自Alfred Hitchcock的"惊魂记"以来，在浴室有可怕新闻，一研究说浴室喷头能隐藏微小细菌，当你洗浴的时候可以喷雾到你的脸上。这对免疫系统正常的人威胁不大，而这些微生物对囊性纤维化或是艾滋病（AIDS）病人、接受癌症治疗或近期器官移植病人就生死攸关了。

科罗拉多大学研究人员测试了5个州的45个浴室，这是在居室、学校和公共建筑中空气和水的微生物学更大研究的一部分。他们报告在国家科学院星期二版公报公布了浴室发现结果。

通常，淋浴有危险吗？主作者Norman R. Pace 说："大概不会，如果你的免疫系统正常的话"."但就像其它事情一样-它也伴随着危险。"

研究者提出警示，所有的金属淋浴喷头，微生物粘附有一定困难。

然而，研究人员注意到淋浴喷头充分隐蔽和有裂隙，使它们清洁困难，甚至用漂白剂处理之后微生物依然存在。人们用过滤淋浴喷头取代每周过滤，合着作者Laura K. Baumgartner说，像阵雨洗澡不会把微生物溅到空气中，而冲击它们形成气雾就容易被吸入。

没有看到1960年代Hitchcock经典电影中淋浴场令人恐惧的着名凶杀。但某些事情和预料完全一致。

涉及某些人肺病有关的分支杆菌（Mycobacterium avium）.

另外，丹佛国立犹太医院研究提出美国近数十年肺部感染增加，其中就有M. avium,按Pace所说这与多淋浴少盆浴者有关。

他说，感染的症状包括疲倦、顽固干咳、呼吸短促、虚弱和全身不适。

纽约、伊利诺斯、科罗拉多、田纳西和北达科他的居室、公寓楼和公共场所的淋浴喷头取样。

研究者从淋浴喷头流水取样，然后移开它们，擦净器具内部并把没有喷头的管中分别取流水样品。

通过样品DNA研究，他们能测定出有细菌存在。

他们发现细菌常常在淋浴喷头中存在，并且比进入给水的细菌要多。

多数水样来自纽约、丹佛城市市政供水系统，但小组也从4个农村家庭私人水井供水的淋浴喷头做了调查。在这些淋浴喷头虽然有一些其它细菌，但没有发现M. avium.

Falkinham还引用其它研究表明，除了免疫系统衰弱者外，有囊性纤维化单个基因的瘦长、老人M. avium感染也有增加，而不是疾病本身。

不在Pace 研究小组的Falkinham说，囊性纤维化需要这基因两个拷贝，而恰好其中一个拷贝能使老人更容易感染M. avium.